This invention relates to coffee and more particularly to the manufacture of soluble coffee.
The manufacture of soluble coffee generally begins with the production of a liquid coffee extract from roasted and ground coffee. A percolator set is normally employed which is a series of extraction columns filled with roasted and ground coffee. An aqueous extraction liquid, generally water, is used to extract the water soluble constituents from the roasted and ground coffee. The percolation process is semi-continuous in that the extraction liquid flows continuously through the extraction columns while the roasted and ground coffee moves batchwise from one cycle to the next, and the extraction liquid is flowed countercurrent to the batchwise movement of the coffee being extracted.
Coffee extract drawn off from the percolator set is generally at a concentration of 20 to 35% soluble coffee solids by weight. This extract is then further processed to dry soluble coffee powder by a number of well-known prior-art processes. Thus, for example, the extract may be passed directly to a spray-drier wherein it is dried to a powder; the extract may be first concentrated to a higher solids content before drying; the extract may be freeze-dried or first concentrated, preferably freeze-concentrated, prior to freeze-drying; the dried powder may be agglomerated before packaging either alone or together with another dry form; various aromas may be removed from the extract and subsequently reincorporated into the dry powder; and other like processes.
Coffee extract is known to contain insoluble or difficultly soluble constituents extracted from the roasted and ground coffee during percolation and usually during the autoclave or hydrolysis portion of the percolation process. These constituents may result in plugging of certain pipe orifices and more importantly may be carried into the final dried powder such that upon reconstitution, specks of insoluble matter appear in the cup, a situation found to be detrimental to consumer acceptance of the product.
Prior art workers, in recognizing this problem, have resorted to varied means of solution. Extract strainers consisting of a porous screen designed to "catch" the insoluble material when the coffee extract is flowed through them have generally proven to be unsuccessful. More commonly, a centrifuge is employed which, while effectively removing the insoluble material also removes valuable coffee solids which may be associated therewith making this method, to some extent, uneconomical. Further, the centrifuge apparatus will usually be quite expensive and require constant cleaning.
The primary object of this invention is to provide a soluble coffee process whereby the final reconstituted coffee product does not contain an undesirable amount of noticeable insoluble or difficultly soluble material.
A further object of this invention is to achieve the aforementioned condition without the need for removal of insoluble or difficultly soluble material from the coffee product.